Papillomaviruses cause warts and other hyperproliferative epithelial disorders in humans and other higher vertebrates (Howley et al., “Papillomaviruses and Their Replication,” In D. M. Knipe and P. M. Howley (ed.), Fields Virology, Lippincott Williams & Wilkins, Philadelphia, 4th ed, vol. 2., pp. 2197-2230 (2001) and Lowy et al., “Papillomaviruses,” In D. M. Knipe and P. M. Howley (ed.), Fields Virology, Lippincott Williams & Wilkins, Philadelphia p. 4th ed, vol. 2., pp. 2231-2264 (2001)). Thus far, more than 130 genetically distinct human papillomaviruses (HPVs) have been identified and/or partially characterized, each with a characteristic tissue tropism and variable disease potential (de Villiers et al., “Classification of Papillomaviruses,” Virology 324:17-27 (2004)). Importantly, several mucosal epitheliotropic HPVs have demonstrated oncogenic potential through close association with anogenital malignancies, including uterine cervical carcinoma (Munoz et al., “Against Which Human Papillomavirus Types Shall We Vaccinate and Screen? The International Perspective,” Int J Cancer 111:278-85 (2004); zur Hausen, H., “Papillomaviruses and Cancer: From Basic Studies to Clinical Application,” Nat Rev Cancer 2:342-50 (2002)). An estimated 500,000 cases and 275,000 deaths from this disease occur annually among women worldwide (Parkin et al., “Global Cancer Statistics, 2002,” CA Cancer J Clin 55:74-108 (2005)).
Long-term efforts by several groups to develop safe and effective vaccines for HPV prophylaxis are now bearing fruit (McNeil, C., “Coming Soon: Cervical Cancer Vaccines, and an Array of Public Health Issues,” J Natl Cancer Inst 98:432-4 (2006)). A tetravalent VLP vaccine formulation (Gardasil™, Merck, Inc.) was approved recently by the U.S. Food and Drug Administration (FDA), and recommended by the Center for Disease Control's (CDC) Advisory Committee on Immunization Practices (ACIP) for universal vaccination of young females (Skjeldestad, F. E., “Prophylactic Quadrivalent Human Papillomavirus (HPV)(Types 6, 11, 16, 18) L1 Virus-Like Particle (VLP) Vaccine (Gardasil™) Reduces Cervical Intraepithelial Neoplasia (CIN) 2/3 Risk,” IDSA Annual Conference, October 7th, San Francisco, USA (2005)). A bivalent VLP formulation (Cervarix™, GlaxoSmithKline), which targets HPV types 16 and 18, is expected to be available soon. Wide-spread use of these vaccines can be expected to lead eventually to a marked reduction in incidence and prevalence of genital HPV disease; however, such an effect will likely require several years to occur, as public and private sector groups work to overcome challenges associated with vaccine distribution, particularly in low-resource settings (“WHO Consultation on Human Papillomavirus Vaccines,” Wkly Epidemiol Rec 80:299-302 (2005)).
Clinical management of genital HPV disease now relies on multiple therapeutic modalities, but all available methods suffer more or less from variable responses to treatment, and variable recurrence rates (ACOG Practice Bulletin, “Clinical Management Guidelines for Obstetrician-Gynecologists No. 61: Human Papillomavirus,” Obstet Gynecol 105:905-18 (2005)). Thus, there is a need for better therapy. The emergence of VLP technology (Hagensee et al., “Self-assembly of Human Papillomavirus Type 1 Capsids by Expression of the L1 Protein Alone or by Coexpression of the L1 and L2 Capsid Proteins,” Journal of Virology 67:315-322 (1993); Kirnbauer et al., “Papillomavirus L1 Major Capsid Protein Self-assembles into Virus-like Particles that are Highly Immunogenic,” Proc Natl Acad Sci USA 89:12180-12184 (1992); and Rose et al., “Expression of Human Papillomavirus Type 11 L1 Protein in Insect Cells: In Vivo and In Vitro Assembly of Viruslike Particles,” Journal of Virology 67:1936-1944 (1993)), which underlies the prophylactic vaccines (Rose, R. C. (ed.), “Human Papillomavirus Immunology and Vaccine Development,” vol. 8. Elsevier, Amsterdam (2002)), has led to the development of several strategies for immunotherapy of established cervical HPV disease (Greenstone et al., “Chimeric Papillomavirus Virus-like Particles Elicit Antitumor Immunity Against the E7 Oncoprotein in an HPV16 Tumor Model,” Proc Natl Acad Sci USA 95:1800-5 (1998); Muller et al., “Chimeric Papillomavirus-like Particles,” Virology 234:93-111 (1997)). Because continued expression of the viral E6 and E7 oncoproteins is required for maintenance of the transformed phenotype, such strategies generally have focused on incorporating viral early (E) proteins into VLPs to promote the induction or enhancement of E protein-specific cellular immune responses. For example, an L1-E7 fusion protein has been shown to self-assemble into chimeric VLPs (cVLPs) that can be used to enhance E7-specific cellular immune responses in mice (Schafer et al., “Immune Response to Human Papillomavirus 16 L1-E7 Chimeric Virus-like Particles: Induction of Cytotoxic T Cells and Specific Tumor Protection,” Int J Cancer 81:881-8 (1999)). In a variation of this theme, L2-E7 or L2-E7-E2 fusion proteins have been generated and incorporated into chimeric VLPs (Greenstone et al., “Chimeric Papillomavirus Virus-like Particles Elicit Antitumor Immunity Against the E7 Oncoprotein in an HPV16 Tumor Model,” Proc Natl Acad Sci USA 95:1800-5 (1998)) that have been shown to provide similar enhancement of E7- and/or E2-specific responses (Schiller et al., “Papillomavirus-like Particle Vaccines,” J Natl Cancer Inst Monogr 28:50-4 (2001)).
In addition to using VLPs for delivery of viral early proteins, VLPs consisting of L1 alone have been shown to be capable of delivering plasmid DNA into cells grown in vitro (Combita et al., “Gene Transfer Using Human Papillomavirus Pseudovirions Varies According to Virus Genotype and Requires Cell Surface Heparan Sulfate,” FEMS Microbiol Lett 204:183-8 (2001) and Touze et al., “In Vitro Gene Transfer Using Human Papillomavirus-like Particles,” Nucleic Acids Research 26:1317-1323 (1998)), in a manner that appears to be somewhat dependent on genotype (Combita et al., “Gene Transfer Using Human Papillomavirus Pseudovirions Varies According to Virus Genotype and Requires Cell Surface Heparan Sulfate,” FEMS Microbiol Lett 204:183-8 (2001)). Interestingly, more recent evidence has suggested that VLPs consisting of both the L1 major and L2 minor capsid proteins may be more efficient for DNA delivery than VLPs consisting of L1 alone (Kamper et al., “A Membrane-Destabilizing Peptide in Capsid Protein L2 is Required for Egress of Papillomavirus Genomes from Endosomes,” J Virol 80:759-68 (2006)). It was shown, for example, that DNA co-delivered with L1 VLPs is retained within endosomes, and that efficient egress from this compartment is dependent on a 23 amino acid sequence located within the L2 carboxyl terminal region. Thus, a potentially important role for L2 in facilitating DNA delivery and expression has been demonstrated in vitro.
It would be desirable to develop a more efficient vaccine that can be used to treat or prevent infectious diseases and various tumors via enhancement of the immune response.
The present invention is directed to overcoming these and other deficiencies in the art.